SGU 275 To xor or not to xor（高斯消元）

//O(60*n)
#include <iostream>
using namespace std;
int n;
long long a[109];

int main()
{
ios::sync_with_stdio();
cin >> n;
long long ans = 0;
for (int i = 1; i <= n; ++i) cin >> a[i];
for (int i = 62; i >= 0; --i) {
for (int j = 1; j <= n; ++j) {
if (a[j] & 1LL << i ) {
long long t = a[j];
if (! (ans & 1LL << i ) ) ans ^= t;
for (int k = j; k <= n; ++k) {
if (a[k] & 1LL << i )
a[k] ^= t;
}
}
}
}
cout << ans << endl;
return 0;
}